This invention relates generally to a device for giving an indication of the speed of a rotating member and particularly to an apparatus for digitizing a sinusoidal signal from an optical tachometer or similar transducer attached to the rotating member.
There is a need to find a system that will accurately digitize a high density sinusoidal signal from an optical tachometer. The working environment is such that the optical tachometer will often present the digitizing system with a relatively noisy sinusoidal signal consisting of spikes and amplitude modulation making it difficult for the system to track the incoming signal especially at high frequencies. Systems using a conventional zero-crossing method are incapable of accurately operating in such an environment.
An additional problem is that the higher the density of the sinusoidal signal, the greater is the need to be able to sense very quickly incremental speed changes. Any delays in reacting to such changes degrade the systems ability to accurately indicate the actual state of the incoming signal at any point in time.